Biographical Sketch: Mario Held has been a performance analyst since 1999, focused on Linux on the mainframe. He is working for the Linux Performance Team at the IBM Boeblingen Laboratory in Germany. He is mostly responsible for compiler GCC and GLIBC performance but also analyzes more general performance items of internal Linux drivers and distributions, too. Prior to joining the performance team, he worked as a systems programmer at IBM and application programmer at a health insurance company in a variety of environments centered on the IBM mainframe. He earned a degree in chemical engineering in 1991 at the Technical University in Merseburg.